A slurry bubble-column reactor is operated by suspending catalytic particles in liquid and feeding gas reactants into the bottom of the reactor through a gas distributor, which produces small gas bubbles. As the gas bubbles rise through the reactor, the reactants are absorbed into the liquid and diffuse to the catalyst where, depending on the catalyst system, they are typically converted to gaseous and liquid products. The gaseous products are recovered from the top of the reactor. Liquid products are recovered from the suspending liquid by using different techniques like filtration, settling, hydrocyclones, magnetic techniques, etc. See Y. T. Shah, et al., AlChE Journal 28(3) (1982) 353-79.
Epoxides such as propylene oxide are important industrial chemical intermediates. An epoxide can be produced by direct oxidation of an olefin with oxygen and hydrogen in the presence of a catalyst (U.S. Pat. Nos. 5,973,171; 7,138,535; 7,238,817; and 7,279,145).
Direct epoxidation of olefins with oxygen and hydrogen is highly exothermic. The reaction selectivity is highly sensitive to the reaction temperature. U.S. Pat. Appl. Pub. No. 20070260075 teaches a tower reactor having a plurality of separate reaction zones wherein the reactant gases are reacted in a slurry of catalyst particles in a solvent. Heat removal zones are provided between the reaction zones. The reactor is suitable for propylene oxide production by reacting propylene, oxygen and hydrogen reactant gases in a liquid medium comprising a slurry of catalyst particles in a solvent such as methanol or methanol and water.